1. Field of the Invention
The present invention relates to an apparatus for injecting a recording solution of a print head, and more particularly to an apparatus for injecting a recording solution of a print head, wherein, a pressure of a liquid chamber is regulated by means of deformation induced during the phase transformation of a thin film shape memory alloy, and the thin film shape memory alloy is buckled while being drawn by a pressure lower than an atmospheric pressure, thereby increasing operating frequency to enhance printing performance, enable to manufacture products of small size and simplify a manufacturing process.
2. Description of the Prior Art
Widely available print heads generally utilize a Drop On Demand (DOD) system. The DOD system has been increasingly employed since the printing operation is easily performed by instantaneously injecting bubbles of recording solution under the atmospheric pressure neither requiring the charge or deflection of the bubbles of the recording solution nor demanding high pressure. A heating-type injecting method using a resistor and a vibrating-type injecting method using a piezo-electric device may be given as the representative injecting principles.
FIG. 1 is a view for explaining the heating-type injecting method, in which a chamber a1 retains a recording solution therein, an injection hole a2 directing from chamber a1 toward a recorded medium is provided, and a resistor a3 is embedded into the bottom of chamber a1 to be opposite to injection hole a2 to incite expansion of air. By this construction, the air bubbles expanding by resistor a3 are to forcibly push the recording solution within the interior of chamber a1 through injection hole a2, and the recording solution is injected toward the recorded medium by the pushing force.
In terms of the heating-type injecting method, however, the recording solution is heated to cause a chemical change. Furthermore, the recording solution adversely adheres onto the inner circumference of injection hole a2 to clog it. In addition to a drawback of short durability of the heat-emitting resistor, the water-soluble recording solution should be utilized to degrade maintainability of a document.
FIG. 2 is a view for explaining the vibrating-type injecting method by means of the piezo-electric device, which is constructed by a chamber b1 for retaining a recording solution, an injection hole b2 directing from chamber b1 toward a recorded medium, and a piezo transducer buried into the bottom of the opposite side of injection hole b2 for inciting vibration.
Once piezo transducer b3 incites vibration at the bottom of chamber b1, the recording solution is forcibly pushed out through injection hole b2 by the vibrating force. Consequently, the recording solution is injected onto the recorded medium by the vibrating force.
Without using the heat, the injecting method by means of the vibration of the piezo transducer is advantageous of selecting a variety of recording solutions. However, the processing of the piezo transducer is difficult and, especially, the installing of the piezo transducer attached to the bottom of chamber b1 is a demanding job to be detrimental to mass production.
Additionally, the conventional print head employs a shape memory alloy for issuing the recording solution. Japanese Laid-open Patent Publication Nos. sho 57-203177, sho 63-57251, hei 4-247680, hei 2-265752, hei 2-308466 and hei 3-65349 disclose examples of print heads employed with shape memory alloys. The conventional examples are constructed to be bending-deformed by joining several sheets of shape memory alloys respectively having different phase transforming temperatures and different thicknesses or by joining an elastic member with a shape memory alloy.
However, the conventional print head using the shape memory alloy involves a difficulty in shrinking the head dimension, an inferior nozzle compactness to degrade resolution and a demanding job in its fabrication, thereby negatively affecting mass production. Also, the shape memory alloy used therein is embodied by a thick layer having a thickness of more than 50 .mu.m instead of incorporating with a thin film. Therefore, it dissipates greater electric power during a heating operation and requires longer cooling time to be disadvantageous of resulting in degraded operating frequency and slow printing speed to have no practical use, etc.